Casting apparatus



May 8, 194:5. H. R. BERGER 2,375,463

CASTING APPARATUS v Filed May 5, 1941 2 Sheets-Sheet 1 Snventor E Havank-r R, Bananen Gttomeg May 8, i945.

H. R. BERGER cAsTING MWAMTUS` Filed May 3, 1941 2 Sheets-Sheet 2 Snnentor HERBERT RuxmaR aux Gttomeg Patented May 8, .1945

CASTING APPARATUS Herbert R. Berger, Brooklyn, N. Y., assignor to J. F. .'ielenko & Co. Inc., New York, N. corporation of New York Application May 3, 1941, Serial No. 391,686

6 Claims.

, This invention relates to casting apparatus of the type intended primarily for use in dental, jewelry or similar` arts. More particularly, said casting apparatus is of the type disclosed in my prior application Serial No. 232,207, filed September 28, 1938, now Patent No. 2,245,065, and my present invention is concerned generally with the provision in apparatus of the type referred to of a furnace of further improved construction and operation.

One object of the invention is the provision of a furnace having an,alundum or other suitable refractory muilie and a carbon crucible mounted in said muiile, the arrangement being such that the crucible is out of contact with the mule except at minor parts of the inner surface of the mulile. 'I'he purpose of this construction and arrangement of the mule and crucible is to prevent such contact between them as would result in carbon from the crucible adhering to or impregnating the muilie to such an extent as to substantially increase the electrical conductivity of the mufe, and also to prevent such contact between the crucible and the muie as would result in current leakage from the muilie to the crucible. In this connection it will be understood y that while alundum has a high electrical resistance within'a temperature range below that at which the furnace operates, the electrical resistance of the mule at the high temperatures at which the furnace operates is greatly decreased and at said high temperatures the alundum muille: is a conductor of electricity and permits current to flow through the carbon crucible when the latter is in contact with the mullle. Furthermore, when the carbon crucible is permitted to contact the mufiie over an appreciable surface area thereof, carbon particles from the crucible adhere to or become impregnated in the mule and increase the conductivity thereof, thereby resulting in the loss of current. These objections and disadvantages are eliminated in accordance with the present invention by maintaining the crucible outof contact with most of the surface area of the muiile.

Another object of the invention is to provide a crucible having a front wall of sufficient depth to prevent the molten metal from spilling through the front or charging opening of the crucible and furnace and further, to provide the muflle and crucible with interengaging means for positioning-the crucible in relation to the mullie so that the lower fron't wall part of the crucible will be in the properr position when the crucible is inserted in the mufiie, it being understood that the crucible is removable from the muffle and replaceable by another crucible of the same or similar construction.

As disclosed in my above mentioned application, the apparatus is provided with a thermocouple positioned adjacentthe inner surface of the muile internally of the latter and connected to a pyrometer for indicating the temperature. In accordance with the present invention the thermocouple instead of being arranged as shown in said application, is disposed within a recessforming part of the mule. Saidrecess-forming part extends longitudinally of the mule and projects radially inwardly of the inner surface of the mutlle, said recess-forming part of the mufiie forming a rib which is received within a groove in the outer surface of the crucible, whereby said rib prevents relative turning movement of said muie and crucible and the thermocouple lies close to the inner peripheral surface of the crucible but is not exposed to the gases or other atmosphere of the crucible. Another object of the invention is to provide a covering for the thermocouple whereby to obviate any impairment thereof. Furthermore, by locating the thermocouple close to the inner surface of the crucible a more accurate indication of the temperature is obtained.

A In centrifugal casting apparatus, molten metal sometimes escapes from between the sprue opening and the mold and flows outwardly between the outlet of the furnace and the inlet of the mold, during the rotation of the furnace for transferring the molten metal from the latter to the mold. Such outward flow of molten metal between the furnace and the mold occurs in a lradial direction and is a source of danger to the operator of the casting apparatus or to anyone in the vicinity of said apparatus during its operation. One ofthe objects of the present invention is to eliminate this danger, this being accomplished pursuant to the present invention by providing the furnace with means for conning and limiting the flow of molten metal in a radial direction.

The above4 and other objects, features and advantages of the invention will best be understood from the following description reference being had to the accompanying drawings, which while illustrating the preferred embodiment of the invention are to be considered as illustrative, but not in limitation, thereof.

' In the drawings:

Fig. 1 is a side View in elevation of a casting apparatus 'embodying the present invention, the

base, and the motor mounted therein being shown in section;

Fig. 2 is a longitudinal sectional view, on a larger scale, of the furnace and of certain parts associated therewith, certain other associated parts being shown in elevation;

Fig. 3 is an elevational View of the crucible;

A, Fig. 4' is a front view on a larger scale of the furnace and of the mounting means therefor, the door of the furnace being shown in open position;

Fig. 5 is a sectional view of the furnace on the line 5--5 of Fig. 4;

Fig. 6 is a front view of the crucible;

Fig. 7 is a rear view of the crucible;

Fig. 8 is a cross sectional view on the line 8 8 of Fig. 3;

Fig. 9 is a fragmentary view of the muflie looking in the direction of line 9 9 in Fig. 4 when the crucible is removed from the furnace.

Referring now more particularly to the drawings the casting apparatus embodying the present invention comprises a base ill in which the spring or other motor i2 is mounted for rotating the shaft ill. A horizontal bar lli is removably secured to the upper end of shaft i4 to rotate therewith. The furnace it is releasably secured to bar iii by a pair of clamping members removably secured by bolts 22 to bar i6 at a poi'nt between shaft i4 and one end of said bar. The furnace is thus supported above the bar, and when it is desired to remove the furnace bolts 22 are removed and the furnace and clamp slid from the bar longitudinally thereof. In order to insure proper location of the furnace, bolts 22 extend through suitable openings in the bar. The upper ends of clamping members 2t are removably secured to the outer casing 2! of the furnace by screws 2t. Clamping members 2li are provided with a pair of arms 28 which extend below bar it at opposite sides, respectively, of the latter. A contact block @il is removably secured between arms 28 by suitable bolts 32.

IThe outer wall 24 of furnace it is preferably formed of sheet metal and is cylindrical, and at its rear end has an outer peripheral ange 35 to which the rear wall 36 of sheet metal is secured in any suitable way preferably by being welded thereto. Said rear wall 36 is provided with an axially extending peripherally continuous flange 3@ provided forthe purpose of preventing the flow beyond a certain point of metal between the outlet of the furnace or heating chamber and the inlet of the mold. A front metal wall 40 provided with a central opening 42 is secured to the front end of cylindrical wall 24 in any suitable way preferably by fastening the peripheral flange it of said front wall to the forward edge of said till) cylindrical wall by means of screws 46 or in any other suitable way.

A cylindrical refractory mule 48, preferably of alundum, is positioned internally of the furnace and forms the inner peripheral wall of the heating chamber, being imbedded at its opposite ends in the front and rear refractory lined walls lill and 52, respectively, which form the opposite end walls of the heating chamber. A heating element 54 composed of an electric resistance winding or windings is disposed around the outer peripheral surface of mule 4B and is covered by any suitable insulating material such as alundum cement 56. A lling 58 of magnesium. asbestos bre or yany other suitable heating insulating material is disposed between the outer surface of heating element 54 and the inner surface of wall 24 of the furnace.

The mufiie 48 has a top part 60 forming a recess in which a thermocouple 62 is positioned, said thermocouple being connected by suitable wiring to two upper contacts 64 on terminal block 30.

The two lower contacts 66 on said terminal block V are connected by suitable wiring to the heating element 54. A movable contact holder 68 is mounted on base l0 and carries contact members which engage the contact members on said block 30 when said holder is projected outwardly, the construction and arrangement being substantially the same as that illustrated and described in my above mentioned application.. It will be understood, that as described in my said application when contact holder 68 is projected outwardly whereby the contact members carried by said holder engage the contact members on block 30 the electric circuits through the heating elements 54 and through the thermocouple and associated pyrometer (not shown) are completed and further that the holder 6B prevents rotation of bar I6 and of the parts carried thereby, and that upon completion of the heating operation, as indicated by the pyrometer as described in said aplication, the movement of contact holder 68 inwardly to disengage the same from block 30 allows rotation of -bar I6.

It will be observed that recess-forming part 60 of the muifle provides a rib which extends longitudinally of the latter from the rear end thereof to a point between said rear and the forward end of the mullie. It will be noted also that said recess-forming part 60 projects radially a short' distance inwardly of the inner surface 'l0 of the muffle, and further that said part 60 of the mule tapers forwardly from its rear end.4 'I'he lower surface of the muffie is provided with a plurality of longitudinally extending peripherally spaced ribs l2, said ribs extending preferably for the full length of said muilie. Ribs 12 support the carbon crucible 14 in position in the furnace out of contact with most of theinner peripheral surface of the muffle, whereby to prevent appreciable Y leakage of current from the muiile to the crucible and to prevent particles of carbon from the crucible from adhering or impregnating the alundum mule.

Crucible 14 is of cylindrical shape and ts removably within the heating chamber of the furnace and more particularly interiorly of muflle 48 but with the outer peripheral surface of the crucible spaced slightly from the inner peripheral surface of the muille., Said crucible has a rear wall 16 and a sprue 18 which projects rearwardly thereof through a central opening Aill) in the rear wall of the furnace. The inner walls of the crucible taper at their rear ends to the opening 82 provided in said sprue and constituting the outlet opening of the furnace. Said crucible has afront wall B4 provided with an inlet opening 86, and by reference more particularly to Figs. 6 and ,8 it will be observed that said opening is formed eccentrically of the front of the crucible so that when the crucible is in 4position in the furnace the lower part 88 of said front wall is deeper than the upper part thereof. The purpose of this construction is to provide the front of the crucible with-a bottom front wall of sumcient depth to prevent spilling of the molten metal, while at the same time permitting an opening of a sufficiently large size to facilitate the placing of the metal in the crucible.

The outer peripheral wall of the crucible is provided with a' longitudinally extending groove 92 which, when the crucible is placed in the furnace, receives the radially projecting part or rib E of the mule, Said groove 92 of the crucible and the recess-forming part 66 of the muie thus form interengaging means to position the crucible properly in the furnace so that the deeper lower part 88 of the crucible is properly positioned at the bottom of the crucible when the latter is mounted in the furnace, said groove 92 of the crucible and said projecting part 60 of the muflle forming interengaging positioning means. Also, it will be noted that rib 6l! prevents relative turning movement between the crucible and the mufiie. Further, it will be noted that by reason of the provision of the groove 92 in the crucible and the projection of recess-forming part 60 into said groove when the crucible is in position in the furnace, the thermocouple is positioned close to the inner surface of the crucible whereby to improve the accuracy of the pyrometer indication.

A flask holder @d is slidably mounted on bar I6 for movement to adjusted positions toward and away from the outlet opening of the furnace. A clamping screw 96 operable by a handle 98 is provided for clamping the holder 9d releasably in adjusted position. A flask or mold l0@ is mounted between the furnace and the holder 9G and is supported on a cradle l @2 which is slidably mounted on bar i6. Cradle W2 supports mold lli@ at the proper height in position to be engaged by the flask holder which holds the forward end of said mold against the outer surface of rear wall 3G, with the sprue opening in registry with the opening in the mold.

The front of the furnace is provided with an insulated hinged door ille which in the closed position thereof engages or lies close to the outer surface of front Wall @d of the crucible. Said door it@ is hinged at tilt to thev front of the metal wall d@ of the furnace and at its lower end is provided with a catch tilt which releasably engages a spring projected holding member lll) carried by bar it; whereby to prevent accidental opening of said door.

As illustrated in Fig. 1 bar l@ is provided with an adjustable counterweight device H2 which is preferably of the construction illustrated in my above described application. Said device H2 has an upwardly extending handle member H5 provided for the purpose of facilitating winding of the spring motor l2 between operations of the casting apparatus.

In the operation of the casting apparatus, the spring motor i2 is rst wound up by grasping handle Ml and rotating bar i6, holding member 68 being in its inwardly retracted position out of contact with the contact members on block 3G and out of engagement with said block. When the spring motor is sufiiciently wound, holding member 58 is projected into the path of block 30 thus preventing rotation of bar I6 and for completing the circuit through the electrical elements and devices through the main switch (not shown) when the latter is closed. It is preferred that a circuit breaker (not shown) be provided for the apparatus to prevent overload ofvthe heating element 5d. The metal to be melted in the furnace is then placed in the crucible and the door closed. Thereafter when the metal in the crucible is melted and the proper temperature is reached as indicated by the pyrometer which is connected Ato the thermocouple, as described above, holder 5% is retracted thereby discontinuing the heating operation and releasing bar l for rotation, but just before the metal is heated to the desired temperature, i. e., at the time the pyrometer is about 25 F. below said desired temperature, the mold is clamped in position inthe apparatus. Preferably said mold is pre-heated in accordance with the usual practice to about 1300D F. when clamped in position, as stated, preliminary to the casting operation. It will be understood that when bar it is rotated by spring motor I2 the centrifugal force thereby generated is effective to transfer the molten metal from the crucible through the sprue opening 82 into the mold |00. It will be observed that if any molten metal shouldl escape between mold Hill and rear wall 36, the peripheral ange 3d of said rear wall will prevent flow of said molten metal beyond said flange and thereby will prevent any injury to the operator or to anyone who may happen to be in the vicinity of the casting apparatus when the latter is operated.

While I have shown and described the preferred embodiment; of my invention it will be observed that the latter might be embodied otherwise than as herein specifically shown or described and further it will be understood that in the illustrated embodiment certain changes in the details of construction and in the arrangement of parts may be made, that certain parts may be used without others, and that other parts may be added; Therefore, I do not wish to be limited to the construction herein specifically shown or described except to the extent which may be required by the scope of the appended claims.

Having thus described my invention, what I `claim and desire to secure by Letters Patent is:

l. In a centrifugal casting machine, means forming a heating chamber and comprising a peripheral Wall, a part of said chamber Wall projecting radially toward the center of the chamber and extending longitudinally thereof and having a recess therein, a thermocouple positioned in said recess, and a "crucible positioned in said chamber and comprising a peripheral wall adjacent said chamber wall, said crucible having a longitudinally extending groove in said peripheral wall thereof into which said chamber wall part projects.

2. In a centrifugal casting machine, means forming a heating chamber and comprising a peripheral wall, a part of said wall projecting radially toward the center of the chamber and extending longitudinally thereof, and a crucible positioned in said chamber and comprising a peripheral wall adjacent said chamber wall, said crucible having a longitudinally extending groove in said peripheral wall into which said chamber wall part projects.

3. In a centrifugal casting machine, means forming-a heating chamber and comprising a cylindrical wall, a crucible positioned in said chamber and having a cylindrical wall adjacent said chamber wall, said crucible having a front wall provided with an opening, the part of said front wall below said opening being deeper than the part of said front wall above said opening, and interengaging means on said two cylindrical walls for preventing relative turning movement therebetween, the last mentioned means .on the chamber wall comprising a projection, said projection on said chamber wall having an internal recess therein, and a thermocouple disposed in said recess and covered by said projection.

4. In a centrifugal casting machine, means forming a heating chamber and comprising aperipheral wall, a crucible mounted in said heating chamber and comprising a peripheral wall disposed adjacent said chamber wall, means. on

one of said walls for preventing appreciable oontactibetween said two wal1's,fsaid meanscomprisy ing a plurality of` peripherally spaced longitudinallyr extending inwardly projecting ribs, means fory holdingy said Crucible' againsty movement laterally of said ribs,` said last' mentioned means comprising a projection on said chamber wall and a recess in said crucible wall in which said projection is received, said projection having a recess closed at -the interior ofthe heating chamber,

and a thermocouple positioned in saidy recess.

said side-wall parts lwhereby the major portions of said side wall partsare held out of contact with yeach other while said crucible is supported by f said side wall of the chamber.

f 6.'In a centrifugal ycasting rmachine1 means forming a heatingr chambery and comprising a side k wall formed of refractory andelectrical-insulation material, acarbon crucible mountedin said chamber in'horizontal position, the lowerl part ofr saidside wall being ina horizontal position, said p Crucible having a side wallfadjacent said side 5*. In a centrifugal casting machine,- means y forming a heating chambery and comprising a side wall formed of refractory and electrical-insulation material, an electric heating element dis#y posed radially outwardly of the rinner surface of chamber in horizontal position, the lower part of y rsaid side w'all, a carbon crucible mounted inr said f said sidewall being in a horizontal position, said V Crucible having' a sidewall adjacent said side wall of the chamber and having a lower part in f 'horizontal position-adjacent to and supported by said lower part of said sidewall of the chamber.

andmeans onone of said side-wall parts integral therewith rprojecting therefrom toward and `en-k f 'gaging the other ofsaidr side-Wall partsr and ofy substantiallyless surface extent than either of ywall of the chamber andr having a lower rpart in horizontal position adjacent to and supported byr v f rparts are held out of contact with each other rwhile said crucible is supported by said side wall of the chamber, the upper parts of said side y f walls having a recess and a projection, respectively, said projection tting into said recess and preventing relative turning movement'of said rside y walls.

f HERBERT R. BERGER. 

